So, inquiring minds are curious. Why was CD-6 only used for the yellow developer? Where the other two color developers substantially changed from what was used in K-12?

Ed

"I only wanted Uncle Vern standing by his new car (a Hudson) on a clear day. I got him and the car. I also got a bit of Aunt Mary's laundry, and Beau Jack, the dog, peeing on a fence, and a row of potted tuberous begonias on the porch and 78 trees and a million pebbles in the driveway and more. It's a generous medium, photography." -- Lee Friedlander

Well, the patent shows CD-4 being used for Cyan and Magenta, but I was told it was CD-3 in K-14. Now, I am confused as well. CD-3 and CD-6 generally yield dyes with better dye stability and better hue for viewing with the human eye. That is why CD-6 was chosen and why I believe that CD-3 is used in the other two developers.

CD-6 was planned for use in the generation of color paper after Ektacolor 70 paper (Ektaprint 3 process in 1969) and in Ektachrome E-6. However, Kodak was sued by Berkey, Pavelle and GAF for coming out with the Ektaprint 3 process and plans for the upgrade to CD-6 were cancelled.

If plans had continued, there is a good chance that RA4 and E6 would be run with CD-6 with even better dye hue and even better image stabilty. You can thank those that sued Kodak, making management nervous about changing processes for this.

However, Kodak was sued by Berkey, Pavelle and GAF for coming out with the Ektaprint 3 process and plans for the upgrade to CD-6 were cancelled.

If plans had continued, there is a good chance that RA4 and E6 would be run with CD-6 with even better dye hue and even better image stabilty. You can thank those that sued Kodak, making management nervous about changing processes for this.

No, the lawsuits by Berkey et. al. were brought on anti-trust grounds. Remember that Kodachrome isn't sold with processing included in the US due to anti-trust suits, there was a consent decree in 1955. It was claimed that Kodak was trying to monopolize film processing by bundling processing with Kodachrome.

There were anti-trust lawsuits about the C-41 process, by large labs who were blindsided by the change from C-22 to C-41. Due to the higher temperatures and shorter times, the labs had to buy new equipment. Again, it was argued that Kodak was changing the developing process just to torture independent processing labs, forcing them to make large capital purchases. Kodak was really just trying to make better film, and the matching processing.

Remember that at the time, Kodak really was the largest processor of color film in the US. (They were just a bit player in B&W.)

Remember also that Kodak did lose a patent lawsuit with Polaroid. There's good arguments that the case was lost due to the judge ignoring the technical arguments. Basically, the judge felt "Polaroid invented instant photography, so ipso facto Kodak is violating their patents, even if they have not violated any claims." Patent lawsuits are often handled abysmally by the courts, it's really a complete gamble to participate in one. (This is one of the reasons US Patent law is such a mess, and Patent Trolls are such a problem.)

(I don't know if Kodak had lost the Polaroid patent case when they decided to punt on further uses of CD-6.)

So, at any rate, Kodak was intimidated by the anti-trust lawsuits, probably particularly the C-41 one, and chickened out on using CD-6 in RA-4 and E-6. A shame.

And, incidentally, the GAF paper went through Kodak's Ektaprint 3 process as well as Kodak paper, but this was ignored by the court. It was judged on the basis of change per se not on any actual damage caused AFAIK.